Electron tube and circuit therefor



g- 1937- H. E. HOLLMANN 2,088,653

ELECTRON TUBE AND CIRCUIT THEREFOR Filed March 8, 1934 INVE NTQR HANS ERlCH HOLLMANN ATTORN EY Patented Aug. 3, 1937 UNITED STATES 7 2,088,653ELECTRON UBE AND CIRCUIT THEREFOR Hans Erich Hollmann, Berlin, Germany,assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic in. b.H., Berlin, Germany, a' corporation of Germany Application March 8,1934, Serial No. 714,651

In Germany March 8,1933

1 Claim. (Cl. 250-36) When a triode tube is operated in what is known asa Barkhausen-Kurz circuit arrangement (retarding-field scheme) the gridis impressed with a high positive potential, Whereas the outer electrodeis connected with a'negativ'e or slightly positive potential; 1 Theelectrons'accelerated by the said high grid potential andfiy ing throughthe grid are retarded in the opposing field of the outer electrode forwhich reason this electrode has come to be called the.retaming-electrode. Supposing that a cathode is used which is operatinginside the range of saturation, then it will be found that the retardingcharacteristic which shows the dependence of the current of theretarding electrode upon the retarding field voltage'is a mirror pictureof the grid characteristic being the inter-relationship between the gridcurrent and the. retarding fieldvoltage.

This so-called Barkhausen-Kurz short wave circuit scheme may be employedfor-the generation, amplification, and rectification of any'desiredfrequencies. Compared with the usual connection of tubes with a positiveouter electrode (anode) and a negatively biased grid, these twoelectrodes, in the Barkhausen-Ku'rz circuit, have not only transposed orinterchanged theirfunc tions as regards potentials, but it has also beensuggested to impress the input voltage between the cathode and the saidretarding electrode, and to connect the output circuit withth e grid.But this scheme is attended withthisdrawback, that the internalresistance between cathode'and retarding electrode is comparatively low,indeed, that it has practically a Value of onlya few hundred ohms, andthis as a result means a considerable load on the source furnishing thecontrol potential.

The present invention is based upon. the idea of increasing the innertube resistance which is in parallel relation with respect to the inputcircuit by connecting two Barkhausen-rKurzQshort wave tubes in series.Asa consequence; the internal resistance is doubled, while the loadofthe source of the control voltage isreduced one half. T

A better understanding oftheinventiohfmay be had by referring to thefollowing detailed description, which is accompanied by drawing wherein:

Fig. 1 shows a fundamental circuit arrangement in accordance with thepresent invention;

Figs. 2 and 3 illustrate, .by way of example, two difierent forms ofelectron tubes having a plurality of anodes with a common grid andcathode for efiecting the object of the invention;

Fig. 4 illustrates a further form of electron tube wherein shields areprovided between two cylindrical anode sections to prevent interactionis varied inversely as the grid current.

between electron streams within the different sections respectively; 1

Fig. 5 shows a modification of the shielding arrangement of Fig. 4where, in this case, semicylindrical anode segments are employed andwhere the shields themselves are disposed in a planewhich intersects theaxis of, the cathode and liesin the gaps between the anode segments;

' Fig. 6 shows a combination of the shielding arrangement of Fig. 5 witha capacitive collar arrangement externally of the tube envelope forvarying the effective inter-electrode capacity;

and

H fFig. 7 shows in cross section a variation in the source of gridvoltage Eg. A circuit arrangement of this kind is serviceable both forthe generation as well as the reception of ultra short waves.

The two retarding electrodes work in phase opposition (push-pull) andthey determine the phase of the potential variations on the electrodesin the two tubes. In the case of a wave generator, the energy is.delivered by the coupling "of an antenna or an energy feed lead in theretarding-electrode circuit. If the arrangement is to be used forreceiving, the retarding-electrode voltage must be so adjusted that theworking point comes to lie about the kneeof the retarding?characteristic.

It is among the features of this invention that Whether the circuit isto be used as a detector,

as an amplifier, or otherwise, the tube characteristics are to beadjusted in such manner that the anode current versus anode voltagegraph forms a mirror picture of the graph constituting the grid currentversus anode voltage. When the adjustment has been suitably made it isfound that the space current, as measured by the number of electronsemitted from the cathode, is maintained constant, while the anodecurrent It is to be understood, however, that when operating a tube inthis manner the operating range is kept within suitable limits ofsaturation. The tube when used as a detector is thus enabled to producerectification in the grid circuit when radio frequency components areapplied in a pushpull manner to the anodes or retarding electrodes.

As a further development of the said basic idea of the invention aspecial form of electron tube is here suggested which is characterizedby a joint cathode and a joint grid, but two or more retardingelectrodes or anodes. However, in order that such a tube may be rendereduseful for the present purposes, it must measure up to otherrequirements, and it distinguishes itself thereby from other similartubes disclosed in the earlier art. In order thatthe effect of allanodes may be the same, and in order that also the length of theelectron paths may be alike, it is necessary that all of the retardingelectrodes or anodes should be located upon the same circular orcylindrical form. "In order to design a push-pull arrangement at leasttwo retarding electrodes must be present. For the sake of insuringuniform field distribution it may also be desirable, however, to providea still greater number of retarding electrodes and to connect the samein two groups. The inter-connections between these groups are mostsuitably established within the vacuum vessel proper, it beingunderstood, moreover, that strict symmetry is essential for the properfunction of such tubes. p

The. formation of the various retarding electrodes is possible in twodifferent ways. .They are either formed by sections at right angles tothe cylinder axis so that two or more co-axial cylinders of likediameter result (Figure 2), or else the cylinder surface is divided, bysections laid through the axis of the cylinder, into segments (Figure3). In order that the conditions of symmetry may be improved in theformer case it may under certain circumstances be advisable to bring themidpoint of the cathode out of the glass bulb and to connectthe'twohalves of the cathode in parallel. Fundamentally speaking, it

- is not necessary that the various retarding electrodes should be oflike size, though when constituting the two electrode groups this pointshould be borne in mind that each of the two groups should have the sametotal surface or area. It would thus be possible, for instance, todispose four co-axial cylinders of like length and like diameteradjacent to one another and to connect the first and the third, and thesecond and the fourth; or else only three cylinders could be provided ofwhich the central one has a length twice that of the two outers, withthe latter two being united together.

Whether this latter arrangement comprising co-axial cylinders, or theone involving segments parallel to the axis, is to be used will dependto a certain degree upon the kind of the oscillation system to beconnected with the tube. Where very short waves are dealt with, say, ofa length below one meter, it has been found that a parallel wire systemis suitable as the oscillation circuit. In this instance, segmentalsubdivision is particularly useful, with the retarding electrodes beingthen placed in the voltage loop of a parallel wire system, i. e., theretarding electrodes are at high potential points on a two wire orlecherwire system, such as shown in Figs. 3 or 6.

To insure undisturbed operation'of the pushpull scheme it is importantthat the electron paths between the cathode and the two retardingelectrodes (or groups thereof) should not interengage. In order toprevent this from occurring the suggestion is made according to thisinvention to'dispose shields or screens in the space between the variousretarding electrodes, said shields or screens consisting preferably ofmetal and being kept at a constant potential. For this purpose theshield is united, for example, with the grid or the cathode.

Figure 4 shows an exemplified embodiment of an arrangement of the saidsort. K is the incandescent cathode, G the grid electrode, and BI, B2,denote the two retarding electrodes having the shape of co-axialcylinders. Between these is disposed the metallic shield S whichconsists of a disk of circular form and which is united with the grid.

In Figure 5 this scheme has been applied to a tube furnished withsegmental retarding electrodes. Under certain circumstances, it may bevery desirable toemploy a unitary metallic gridsupporting element Swhich of itself constitutes the shielding surfaces.

The two retarding electrodes (or groups thereof) are to be regarded asthe coats or plates of a condenser between which a certain potentialprevails. According to another object of this invention, the saidcapacity is utilized for the purpose of tuning the oscillation circuitbetween the retarding electrodes to resonance. In order that theeffective capacity may be varied, recourse is bad according to thisinvention to an arrangement as shown in Figure 6 which has provedpreferable for short wave work. The two retarding electrodes El, B2 arelocated at close proximity to the inner wall of the cylindrical glassbulb Z or i are made to bear directly thereon. 'A metallic collar T ismounted on the outside of the glass of which are formed, on the onehand, by the said metallic tube, and, on the other hand, by theretarding electrodes BI and B2. It can be seen. directly that thecapacity of these condensers is increased, the farther the said tube Tis shifted over the electrodes. in Fig. 6 also includes preferably apair of shield plates S lying in a plane which intersects the axis ofthe cathode and passes through the gaps between the anode segments.

Instead ,of a metal tube T, metallic rotatably mounted on the glass bulbcould be arranged as shown in Figure 7. If these are turned in adirection as indicated by the arrow p, the capacity between theretarding electrodes Bl B2,

The structure shown coats S and the coats S will be obviously altered.The

number of the outer electrodes S should suitably be the same as thenumber of retarding electrodes B.

I claim:

.An electron discharge device having a vacuumtight envelope, a centrallydisposed linear cathode, a cylindrically formed screen electrodecompletely surrounding said cathode, a plurality of anode segmentshaving cylindrical surfaces of the same radius co-axially disposed aboutsaid screen electrode, shielding means interposed between adjacent edgesof said anodesegments and connected to said screen electrode, aninductive circuit interconnecting said anode segments, and.

means including a metallic collar adjustably fit-

